Do Keep your collection organized.  This will help you find the card you are looking for.

Don't bother to alphabetize them.  When you add more cards this just creates a logistical nightmare.

Do Protect your cards by placing them in boxes, binders, and card condoms.

Don't eat or drink around your collection.  Wash and dry your hands before you handle bare cards.

Do use recommended, high quality, acid free "card condoms" when playing with valuable cards.

Don't laminate them.  This will destroy the value of the card.

Do buy cards from the guild to raise money for tournaments and other activities.

Don't mortgage your house to do it.